The technology relates to a secondary battery-use anode including an anode active material that inserts and extracts an electrode reactant at a potential (a potential to lithium) of 1 V to 3 V both inclusive. The technology relates to a secondary battery that uses the secondary battery-use anode. The technology relates to a battery pack, an electric vehicle, an electric power storage system, an electric power tool, and an electronic apparatus that use the secondary battery.
Various electronic apparatuses such as mobile phones and personal digital assistants (PDAs) have been widely used, and it has been demanded to further reduce size and weight of the electronic apparatuses and to achieve their longer lives. Accordingly, batteries, in particular, small and light-weight secondary batteries that are able to achieve high energy density have been developed as power sources for the electronic apparatuses.
In these days, applications of the secondary battery are not limited to the electronic apparatuses described above, and it has been also considered to apply the secondary battery to various other applications. Examples of such other applications may include: a battery pack attachably and detachably mounted on, for example, an electronic apparatus; an electric vehicle such as an electric automobile; an electric power storage system such as a home electric power server; and an electric power tool such as an electric drill.
There have been proposed secondary batteries that utilize various charge and discharge principles in order to obtain battery capacity. In particular, attention has been paid to a secondary battery that utilizes insertion and extraction of an electrode reactant, because such a secondary battery is able to achieve high energy density.
A secondary battery includes a cathode, an anode, and electrolytic solution. The cathode includes a cathode active material that inserts and extracts an electrode reactant, and the anode includes an anode active material that inserts and extracts the electrode reactant. The electrolytic solution includes a solvent and an electrolyte salt.
As the anode active material, carbon materials such as graphite have been widely used, and metal-based materials such as silicon have been also used in applications needing high capacity. In addition, in order to reduce volume change of the anode active material during charge and discharge, high-potential materials such as lithium-titanium composite oxide have been used. The high-potential materials have a high insertion-extraction potential to an electrode reactant.
For example, a cylindrical type battery structure using a battery can as a member containing the cathode, the anode, and the electrolytic solution has been widely adopted as the battery structure of the secondary battery. A laminated film type battery structure using a laminated film such as an aluminum laminated film has been adopted in applications needing battery shape variability.
Since these secondary battery structures largely influences battery characteristics, various considerations have been made on the structure of the secondary battery.
More specifically, in order to increase battery capacity, the cathode includes an oxidizable agent such as lithium-2-hydroxypropionate (refer to, for example, Patent Literature 1). In order to suppress deterioration of load characteristics, a lithium salt such as lithium 2-hydroxybutanoate is used as an electrolyte salt (refer to, for example, Patent Literature 2).
In addition, in order to achieve superior charge-discharge cycle characteristics and in order to suppress gas generation inside the battery, the cathode includes, for example, lithium 4-hydroxybutyrate or lithium 2-hydroxypropane sulfonate (refer to, for example, Patent Literature 3).